* {
    margin: 0;
    padding: 0;
}

.container {
    position: relative;
    width: 533px;
    height: 300px;
    margin: 0 auto;
}

.item {
    opacity: 0;
    transition: opacity 1s;
    position: absolute;
}

.item.active {
    opacity: 1;
}

.circles {
    position: absolute;
    right: 50px;
    bottom: 40px;
    list-style: none;
    overflow: hidden;
}

.circle {
    float: left;
    width: 15px;
    height: 15px;
    border-radius: 50%;
    background-color: #fff;
    margin: 0 4px;
}

.circle.on {
    background-color: orange;
}

.btn-left:hover,
.btn-right:hover {
    background-color: rgba(255, 255, 255, 0.5);
}

.btn-left,
.btn-right {
    width: 54px;
    height: 79px;
    cursor: pointer;
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
}

.btn-left {
    left: 20px;
    background: url(../images/pre.png);
}

.btn-right {
    right: 20px;
    background: url(../images/next.png);
}